Temperature limiting system for a spring loaded torque limiting clutch

Abstract

A temperature responsive fuse is provided for use in a vacuum cleaner brush dowel drive clutch mechanism to prevent overheating of the clutch mechanism upon a continued rotation of the drive belt after the brush dowel has stalled due to jamming or similar occurances. The friction clutch is provided to prevent damage to the cog drive belt if the brush dowel becomes stalled and the fuse, which is a meltable spacer positioned between a loading spring and the engaging friction drive surfaces, is provided to prevent excessive heat build-up in the clutch mechanism in case a safety circuit, which normally detects stoppage of the brush dowel and deenergizes the dowel drive motor, should fail. The fuse spacer will melt at a temperature in the range of 300° F. to 400° F. to unload the spring thereby reducing friction between the engaging surfaces of the clutch mechanism and thus lowering the amount of heat generated.

We claim as our invention: 
     
       1. In a vacuum cleaner, the combination comprising: a brush dowel rotatably mounted to engage a floor surface to be cleaned;   an electric drive motor with an output shaft drivingly engagable with said brush dowel to rotate said brush dowel;   a drive belt connecting said output shaft and said brush dowel providing said driving engagement;   a clutch mechanism on said brush dowel between said brush dowel and said drive belt to prevent damage to said drive belt if said brush dowel is restrained against rotation;   said clutch mechanism including a loading spring;   a plurality of engaging surfaces having a sufficiently large friction therebetween when pressed into engagement by said loading spring to transmit sufficient torque from said drive belt to said brush dowel to cause said dowel to rotate against said floor surface, said engaging surfaces having a sufficiently small friction therebetween to cause slippage therebetween when said dowel is held against rotation while said drive belt continues to rotate, and   a fuse spacer positioned between said spring and said engaging surfaces, said fuse spacer having a melting temperature in the range of 300° F. to 400° F.; whereby, said fuse spacer will melt and release the spring force of said spring upon continued slippage between said engaging surfaces to prevent an undesirable temperature build up in said clutch mechanism.     
     
     
       2. A device according to claim 1, wherein said fuse spacer is positioned adjacent a gap between said spring and said engaging surfaces such that when said spacer melts it will flow into said gap to provide a visual indication to users of said device that the fuse needs to be replaced. 
     
     
       3. A device according to claim 2, wherein said fuse spacer is fabricated of a distinctly colored material to enhance the visibility of the material upon its flowing into said gap. 
     
     
       4. A device according to claim 1 including a pulley member carried on said brush dowel to be drivingly engaged by said drive belt and said engaging surfaces being positioned between said pulley member and said brush dowel. 
     
     
       5. A device according to claim 4, wherein said drive belt comprises a cog drive having teeth and said pulley comprises a sprocket with ridges for meshing with said drive belt teeth. 
     
     
       6. A device according to claim 4 including a plurality of washers and friction facing members carried on said brush dowel and engagable with said pulley to provide said engaging surfaces. 
     
     
       7. A device according to claim 6, wherein said engaging parts including said dowel, said washers, said friction facings, said pulley and said fuse spacer have beveled engaging surfaces such that said engaging parts are self-centered with respect to each other. 
     
     
       8. A device according to claim 7, wherein said loading spring is a coil spring carried on said brush dowel. 
     
     
       9. In a vacuum cleaner a floor engaging brushing apparatus comprising: a wheeled floor engaging housing for rolling over a floor surface to be cleaned;   an electric motor mounted in said housing and having an extending drive shaft with a sprocket-type driven pulley thereon;   a brush dowel rotatably mounted in said housing;   a sprocket member carried on said brush dowel;   a cog drive belt mounted on said sprocket-type drive pulley and said sprocket member to transmit a drive torque from said motor to said sprocket member;   a clutch mechanism positioned between said sprocket member and said brush dowel to transmit said drive torque from said sprocket member to said brush dowel; said brush dowel having a removable end piece carried on a reduced diameter shaft portion of said brush dowel, said brush dowel having a beveled surface providing a transition to said reduced diameter shaft;   said clutch mechanism comprising a first cone washer having a central opening for being received on said shaft portion and being engagable against said beveled surface;   a first friction facing member engagable against said first cone washer and said sprocket member;   said sprocket member having a central opening for being received on said shaft portion and defining a pair of beveled surfaces, a first of said surfaces engagable with said first friction facing material to urge said material against said cone washer;   a second friction facing material engagable with a second of said beveled surfaces;   a second cone washer having a central opening for being received on said shaft portion and being engagable with said second friction facing material;   a fuse spacer member fabricated of a material with a melting temperature in the range of 300° to 400° F. having a central opening for being received on said shaft portion and having a first beveled end for engaging said second cone washer to urge said cone washer against said second facing material;   a coil type load spring carried on said shaft portion having a first end engagable against said fuse spacer member;     said removable end piece of said brush dowel having an opening for being received on said shaft portion with an end wall for engaging and pressing against said spring to load said spring;   said removable end piece being removably retained on said shaft member by means of a locking fastener;   said friction facings, cone washers and sprocket having a sufficiently large friction therebetween when pressed into engagement by said load spring to transmit sufficient torque from said sprocket member to said brush dowel to cause said brush dowel to rotate against said floor surface, said friction facings, cone washers and sprockets having a sufficiently small friction therebetween to cause slippage therebetween when said dowel is held against rotation while said drive belt continues to rotate; whereby, said fuse spacer will melt and release said load from said spring upon said slippage causing a rise in temperature of said clutch mechanism to a level above said melting temperature of said fuse to prevent a temperature rise in said clutch mechanism appreciably above said melting temperature.       
     
     
       10. An apparatus according to claim 9, wherein said fuse spacer is positioned adjacent a gap between said second cone washer and said removable dowel end piece such that when said spacer melts it will flow into said gap to provide a visual indication to users of said apparatus that said fuse needs to be replaced. 
     
     
       11. A device according to claim 10, wherein said fuse spacer is fabricated of a distinctly colored material to enhance the visibility of the material upon its flowing into said gap.